We do not know when man first began to use salt, but we do know that it has been used in many different ways throughout history. Historical evidence shows, for example, that people who lived over 3,000 years ago ate salted fish. Thousands of years ago in Egypt, salt was used to preserve (保存) the dead.

    Stealing salt was considered a major crime (罪行) during some periods of history. In the eighteenth century, for example, if a person was caught stealing salt, he could be put in prison and his ears could be cut off.

    In the Roman Empire, one of the most important roads was the one that carried salt from the salt mines to Rome. Guards were stationed(安置) along the route to protect against salt thieves, and they received their pay in salt, thus bringing the English word, salary. Any guard who fell asleep while on duty was thought to be “not worth his salt”, and as a result he would get a little less salt on his next payday. The expression, “not worth his salt”, is still used today in English.

    In the modern world salt has many uses beyond the dining table. It is used in making glass and airplane parts, in the growing of crops, and in the killing of weeds (杂草). It is also used to make water soft, to melt (融化) ice on roads and highways, to make soap, and to fix colors in cloth.

    Salt can be got in various ways besides being taken from mines underground. Salt water from the ocean, salt water lakes or small seas can be used to make salt. Yet, no matter where it comes from, salt will continue to play an important role in the lives of people everywhere.

    People often ask which is the most difficult language to learn, and it is not easy to answer because there are too many factors to take into consideration. Firstly, in a first language the differences are unimportant as people learn their mother tongue naturally, so the question of how hard a language is to learn only makes more sense when learning a second language.

    A native speaker of Spanish, for example, will find Portuguese much easier to learn than a native speaker of Chinese, for example, because Portuguese is very similar to Spanish, while Chinese is very different, so first language can affect learning a second language. The greater the differences between the second language and our first, the harder it will be for most people to learn. Many people answer that Chinese is the hardest language to learn, possibly influenced by the thought of learning the Chinese writing system, and the pronunciation of Chinese does appear to be very difficult for many foreign learners. However, for Japanese speakers, who already use Chinese characters in their own language, learning writing will be less difficult than for speakers of languages using the Roman alphabet.

    Some people seem to learn languages easily, while others find it very difficult. Teachers and the circumstances in which the language is learned also play an important role, as well as each learner's motivation for learning. If people learn a language because they need to use it professionally, they often learn it faster than people studying a language that has no direct use in their day to day life.

    Obviously , British diplomats and other embassy staff have found that the second hardest language is Japanese, which will probably come as no surprise to many, but the language that they have found to be the most problematic is Hungarian, which uses a similar alphabet to English but has 35 cases (forms of a nouns according to whether it is subject, object, genitive, etc). This does not mean that Hungarian is the hardest language to learn for everyone, but it causes British diplomatic personnel, who are generally used to learning languages, the most difficulty. However, Tabassaran, a Caucasian language has 48 cases, so it might cause more difficulty if British diplomats had to learn it.

    Different cultures and individuals from those cultures will find different languages more difficult. Therefore, it is impossible to say that there is one language that is the most difficult language in the world.

    There are many events you can do in our city. Now have a look at them.

    Mindfulness Meditation（冥想）: Learn how just five minutes a day of meditation can benefit emotional, mental and physical health. The Hernando County Public Library System will host this seminar, which introduces some meditation techniques. Presented by Diana Reed of Gaya Jyoti Yoga. 1:30 pm to 2:30 pm. Free. S. T. Foggia Branch Library, 6335 Blackbird Ave, Spring Hill.（352）754-4043.

    Book Discussion Group: Each month, the group discusses a new book. The group is designed for adults. This month's book is The End of Your Life Book Club by Will Schwalbe. Contact the library for a copy of the book and discussion questions. 1:45 pm to 3: 15 pm. Free. Harold G. Zopp Memorial Library, 9220 Spring Hill Drive, Spring Hill.（352）754-4043.

    What to Do When Your Landscape Sleeps: Seminar participants will learn how to care for a landscape during the cool season and prepare it for spring and summer. 10: 30 am. Free. Harold G. Zopp Memorial Library, 9220 Spring Hill Drive, Spring Hill.（352）540-6230.

    Writers Workshop: The group meets every other Thursday. All levels of experience from beginners to published authors are welcome. Bring pen and paper. 1 pm to 3 pm. Free. East Hernando Branch Library, 6457 Windmere Road, Ridge Manor West.（352）754-4043.

    Low-cost Pet Vaccination（预防接种）Clinic: Sponsored by the Florida International Teaching Zoo veterinary（兽医）staff. Vaccinations are administered by a veterinarian. 6: 30 pm to 7: 30 pm. Rabies vaccinations for dogs and cats are $ 7. Tractor Supply Go. , 18471 Cortez Blvd, Brooksville. (352) 867-7788.

    The UK has a whole host of things to do for free or at a low price and there are a number of websites devoted to bringing you the best. Take a look at our guide to some of our favorite UK cities.

    London

    If you live in or near London and have access to the Internet, you'll discover many choices of free entertainment. The Londonist is an amusing website that offers daily and weekly breakdowns of the free and cheap events in the city. Categories include art, comedy, music, food and drink, theatre, festivals and talks. Head over to Londonist.com for the latest schedule of affordable entertainment. Time Out's website (Timeout, com/London) also has lots of information about free fun in the lively capital.

    Find out why the 60s really cemented(巩固) London as counterculture capital of the UK in our shop.

    Manchester

    Manchester is probably one of the top creative centers of England (if not the UK). If you need any further convincing evidence, then head over to Creative Tourist, where you can find bags of daytime and nighttime entertainment that's easy on the pocket. While you're there you can also check out Liverpool and Sheffield.

    Manchester is a historical city, which has shaped life in Britain. Take a look in our shop.

    Glasgow

    If Manchester is the creative center of England then Glasgow has to be the creative center of Scotland. You can visit Scotland's Center for Design and Architecture at The Lighthouse, or go over to the Gallery of Modem Art, and then there's the wonderful and strange Hunterian Museum. For a lowdown on the best free of Glasgow, take a look at VisitScotland.

    For a look at Glasgow's picturesque qualities click here.

    What's it like to become a music star with millions of fans? These young artists know the feeling. Over the course of their short careers, they have attracted the attention of the biggest stars in the world and taken home prizes from major shows. For now they're just kids that everyone in music is watching. Check out the next generation of stars below.

    FIFTH HARMONY

    The 1990s was a brilliant period for girl groups. But after that few groups have been able to make much of an influence. This doesn't seem to bother Fifth Harmony, who landed the biggest hit of their career in 2016 with "Work from Home", a pop song that encourages everyone to ask for leave more often. When it climbed to No.4 on the Billboard Hot100, it was the first time that a girl group had entered the top 5 in the past ten years.

    LORDE

    It's been four years since the release of Born Heroine — the hot selling CD that made her a 16-year-old global sensation and the spokeswoman for a new generation of smart, strong-minded, creative female pop artists. She contributed to The Hunger Games soundtrack (插曲) in 2014, and for this time setting foot in Hollywood production also brought her more opportunities in her following career.

    TROYE SIVAN

    You might recognize the rising star Troye Sivan from YouTube, where he's been uploading videos since he was 12 and his channel already has millions of fans, or from the movies, where he played the role of young Wolverine in X-Men Origins: Wolverine.

    Let us all raise a glass to AlphaGo and the advance of artificial intelligence. AlphaGo, DeepMind's Go-playing AI, just defeated the best Go-playing human, Lee Sedol. But as we drink to its success, we should also begin trying to understand what it means for the future.

    The number of possible moves in a game of Go is so huge that in order to win against a player like Lee. AlphaGo was designed to adopt a human—like style of gameplay by using a relatively recent development--deep learning. Deep learning uses large data sets," machine learning" algorithms （计算程序） and deep neural networks to teach the AI how to perform a particular set of tasks. Rather than programming complex Go rules and strategies into AlphaGo DeepMind designers taught AlphaGo to play the game by feeding it data based on typical Go moves. Then, AlphaGo played against itself, tirelessly learning from its own mistakes and improving its gameplay over time. The results speak for themselves.

    Deep learning represents a shift in the relationship humans have with their technological creations. It results in AI that displays surprising and unpredictable behaviour. Commenting after his first loss, Lee described being shocked by an unconventional move he claimed no human would ever have made. Demis Hassabis, one of DeepMind's founders, echoed this comment:"We're very pleased that AlphaGo played some quite surprising and beautiful moves."

    Unpredictability and surprises are—or can be—a good thing. They can indicate that a system is working well, perhaps better than the humans that came before it. Such is the case with AlphaGo. However, unpredictability also indicates a loss of human control. That Hassabis is surprised at his creation's behaviour suggests a lack of control in the design. And though some loss of control might be fine in the context of a game such as Go, it raises urgent questions elsewhere.

    How much and what kind of control should we give up to AI machines? How should we design appropriate human control into AI that requires us to give up some of that very control? Is there some AI that we should just not develop if it means any loss of human control? How much of a say should corporations, governments, experts or citizens have in these matters? These important questions, and many others like them, have emerged in response, but remain unanswered. They require human, not human - like, solutions.

    So as we drink to the milestone in AI, let's also drink to the understanding that the time to answer deeply human questions about deep learning and AI is now.